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2 Materials Science Poland

2 2007

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Properties of extended Hubbard models with anisotropic spin-exchange interaction

Czart W. R., Robaszkiewicz S.

Materials Science Poland

2007

Vol. 25, No. 2

485--489

The phase diagrams and electron orderings of the half-filled extended Hubbard models with anisotropic spin-exchange interactions are studied. The cases of ferromagnetic and antiferromagnetic exchange couplings are considered for repulsive on-site interaction (U ? 0). The analysis of these t-U-J||-J??models is performed for d-dimensional hypercubic lattices including d = 1 and d =??by means of the (broken symmetry) HFA supplemented, for d = ?, by the slave-boson mean-field method. The basic features of the derived phase diagrams are discussed.

Phase diagrams and properties of the ground state of the anisotropic Kondo lattice model

Sidowski M., Robaszkiewicz S.

Materials Science Poland

2007

Vol. 25, No. 2

479--483

The properties of the half-filled Kondo lattice model with anisotropic intersubsystem exchange interaction JXY and JZ are discussed. The phase diagram and ground state characteristics of the system are determined within a variational mean-field approximation for the case of rectangular density of states (DOS) for itinerant electrons. The ground state phase diagram is found to exhibit five different phases: Kondo singlet state, two planar antiferromagnetic phases, and two Ising antiferromagnetic (Néel) phases.